1. Field of the Invention
The present invention relates to a simplified direct method for the preparation of transition metal complexes of 2,2'-thiobis(alkylphenolates) with hydroxy- organic ligands wherein the initial hydroxyorganic ligand is employed both as a reactant and as a solvent. These transition metal complexes such as, for example, nickel (II) thiobis-(alkylphenolates) when complexed with hydroxyl-substituted ligands such as alcohols and phenols may be added to organic compositions, normally subject to oxydative degredation such as lubricants and plastics, to impart anti-oxidant and ultra-violet stabilization thereto.
2. Brief Description of the Prior Art
The production of lubricant compositions, for example, lubricating oils produced by hydrocracking provides a relatively high viscosity index oil and permits the use of base stocks that would be unsuitable for other purposes. On the other hand, however, hydrocracked lubricating oils tend toward poor stability against ultra-violet light degradation, rapidly forming suspended and/or precipitated insoluble material on exposure to ultraviolet light, such as sunlight, or other sources of actinic radiation. Additionally lubricants may be subjected to high temperatures which tend as mentioned heretofore to catalyze oxidative degradation.
Commercially available ultraviolet stabilizers are listed by class and function and identified as to structure in the Kirk-Othmer Encyclopedia in "Encyclopedia of Chemical Technology"; Second Edition, Vol. 21, pp. 115-122. U.S. Pat. No. 3,832,304 dicloses the use of aromatic azo compounds for stabilizing hydrocracked oils. U.S. Pat. Nos. 2,703,786; 2,716,090 and 3,210,277 disclose the use of polyvalent metal, e.g., Ni salts of thiobis(alkylphenols) as oxidation inhibitors and plasticizing agents. Nickel thiobis-(4-t-octylphenolate) is disclosed in U.S. Pat. No. 2,971,940 as a stabilizer for plastics and complexes thereof with amines, e.g., n-butylamine are disclosed in U.S. Pat. No. 3,215,717 as plastic stabilizers.
Additionally, in the prior art, transition metal phenolate complexes of 2,2'-thiobis(alkylphenols) which have hydroxyorganic ligands have been employed as stabilizers for a wide variety of lubricants, greases, and plastics. For example, nickel complexes have been found useful in stabilizing plastics such as polyolefins against the deteriorative action of ultraviolet light. When employed with lubricants, such additives also have a stabilizing effect in that they prolong the useful life of a lubricant by increasing its resistance to oxidation.
In the past, methods have been disclosed in the prior art for the preparation of such transition metal phenolates of 2,2'-thiobis(alkylphenol) in a first step to produce the transition metal complex of the 2,2'-thiobis(alkylphenol). The resultant metal complex is subsequently reacted with the desired hydroxyorganic ligand to form the final transition metal complex. Such prior art includes U.S. Pat. Nos. 3,313,770, and 4,198,303, the disclosures of which are incorporated herein by reference wherein it is taught that to form the desired transition metal complex a 2,2'-thiobis(alkylphenol) is reacted with a nickel compound such as nickel nitrate to eventually form the nickel 2,2'-thio- bis(alkylphenol) which is then subsequently reacted in a separate step with the hydroxyorganic ligand to form the desired transition metal complex.